The present invention relates generally to data storage systems and more particularly relates to tape drive emulation (TDE) systems.
Many data processing systems utilize tape drives for storage of data. Channel interfaces and commands generated by a data source to control the transfer of data from a host computer to a tape drive are well-known in the art and will not be described in detail here. One example of an operating system for managing data transfer between a host computer and a tape drive is the MVS system manufacture by IBM Corporation.
In a tape drive emulation system, the data output by the host is not actually written to a tape drive and data input by host is not actually read from a tape drive. Instead, in one type of TDE system, the data is input from and output to staging disks.
According to one aspect of the invention, an improved interface facilitates communication between a library management system (LMS), operating on a host computer, and an Open Systems Server (OSS) containing virtual tape drives (VTDs) and operating as a TDE system.
According to another aspect of the invention, the interface supports two different kinds of communications. One type is a dump of a large amount of data that is not suitable to real-time short transactions. In this case, the data to be provided to the LMS is packaged in a virtual volume with a special name convention. Such a special virtual volume is called an xe2x80x9cadministrative volume.xe2x80x9d Periodically, the LMS requests an administrative volume, the OSS xe2x80x9cmountsxe2x80x9d the volume on a VTD, and the LMS reads the wanted information from the VTD. Thus, the administrative volume is used to communicate status, control, and configuration information between the LMS in the host and OSS, using a standard access method (tape or virtual tape).
According to another aspect of the invention, the interface utilizes load display (LD) commands. LD commends are channel commands normally used to route messages to a tape drive""s operator display accessory. The present invention utilities LD commands to communicate policy and control information messages to the TDE system and to monitor its condition. Policy information reflects decisions by the user(s) and includes rules and preferences for the handling and disposition of data written to VTDs. These user decisions are unknown to OSS, but are communicated to the LMS in the host, and guide LMS in its operation. For example, the assignment by LMS of particular data to a virtual volume belonging to a virtual volume set (VSET) with which a collection of pre-programmed handling rules is associated is an expression of policy. The virtual volumes need a large amount of policy info for management.
According to another aspect of the invention, the SBUS card slots are expanded to facilitate the use of a SPARC CPU to control a mass storage system.
According to another aspect, a special xe2x80x9cHealth Checkxe2x80x9d LD message is periodically sent. If a critical situation exists within OSS, a special error message will be generated and delivered to the operator by LMS.
According to another aspect of the invention, SBUSs of two SPARC CPUs are connected to each ESCON interface for redundancy.
Additional features and advantages of the invention will be apparent in view of the following detailed description and appended drawings.